UPM Energy has brought a new 6MW ultracapacitor system online at its Kuusankoski hydropower plant on the River Kymi in Kouvola, Finland. The device stores energy and delivers fast balancing power to the electricity grid. The company says demand for rapid and flexible balancing capacity has grown alongside the increased use of weather-dependent renewable energy.
The project, first announced in August 2024, triples UPM’s ultracapacitor capacity. According to the company, the system can react to grid-balancing needs in a fraction of a second. Ultracapacitors are described as maintenance-free and longer-lasting than batteries.
“The need for reserves has tripled in the last five years, due to the increased share of weather-dependent energy sources. When there is no wind, balancing power is needed, which hydropower in particular can provide,” said Juha Haromo, Development Manager at UPM Energy. “Ultracapacitors provide a rapid response, complementing hydropower and helping to ensure the durability of power plants. This means more balancing power for the grid and better balance for the entire electricity system.”
UPM says the Kuusankoski installation uses digital tools and automation to optimise both the ultracapacitor and hydropower operations, supporting reliable grid services.
The company’s first ultracapacitor was deployed in 2022 at the Ontojoki hydropower plant, which it describes as the world’s first combination of a hydropower system and an ultracapacitor.
UPM Energy is Finland’s second-largest electricity producer, with 99% of its output reported as emission-free.
The Kuusankoski hydropower plant was built in the late 1940s. It has undergone several major renovations, including a comprehensive modernisation that improved its efficiency to 94% and increased turbine capacity to about 37 MW. The upgrade raised average annual electricity production to approximately 195 GWh. The plant’s three turbines and generator units have been renewed, along with its automation, protection systems and a main transformer, and its backup power system has been strengthened.
